FIELD OF THE INVENTION
This invention relates generally to biodegradable drug dosage forms that can be implanted beneath the skin of mammalian subjects, with particular application to the implantation of such dosage forms at the site of surgical incisions.
Infection at the site of surgical incisions is a common and dangerous hazard associated with surgical operations. Such infection is often controlled and prevented, however, by the systemic administration of antibiotics to the patient after the surgery. These antibiotics are administered both orally in the form of pills, and parenterally, and carried throughout the body and through the bloodstream, with only a fraction of the drug actually reaching the site of the surgical incision and having its intended effect. Because so little of the administered antibiotic actually reaches the site of the surgical incision to prevent infection, much more of the antibiotic than is actually necessary must be prescribed and ingested. Even with these large amounts of prescribed antibiotic, however, infection remains a substantial risk. What is needed is a local method to deliver the antibiotic only to the localized area where the risk of infection is greatest.
Moreover, there is needed a method to deliver the antibiotic locally, in a form other than a liquid solution. While local administration of a drug in solution form provides high local concentration of the drug at the site of the surgical incision, the drug is delivered and absorbed instantaneously, and the effect of the drug therefore quickly diminishes. What is needed, therefore, is a method of locally administering a drug in which the drug is delivered to the local area over an extended period of time.
A biodegradable dosage form which could be implanted at the site of a surgical incision to release a drug over an extended period of time, could be one such method. Such a dosage form, and method of using such dosage form, could be used to deliver many types of drugs in which local delivery of the drug is beneficial.
There is provided by the invention a method to administer a drug locally to a subject in which biodegradable dosage forms that contain the drug are implanted at a localized site beneath the skin of the subject whereupon the dosage forms release the drug over a desired period of time at a substantially continuous rate. Compositions that accomplish the method are also provided. Compositions are further provided that affect the release profile or release duration of drugs that are released from the compositions, as are methods that employ these varying release profiles to provide implantable dosage forms that release drugs at a prescribed rate over a prescribed period of time. The compositions are particularly well adapted to implantable dosage forms because they biodegrade quickly to an acceptable level after delivering the drug.